The present invention relates generally to chemical formulations useful in semiconductor manufacturing and particularly to chemical formulations that are utilized to remove residue from wafers following a resist plasma ashing step. More specifically, the present invention relates to cleaning formulations for removal of inorganic residue from semiconductor wafers containing delicate copper interconnecting structures.
The prior art teaches the utilization of various chemical formulations to remove residues and clean wafers following a resist ashing step. Some of these prior art chemical formulations include akaline compositions containing amines and/or tetraalkyl ammonium hydroxides, water and/or other solvents, and chelating agents. Still other formulations are based on acidic to neutral solutions containing ammonium fluoride.
The various prior art formulations have drawbacks that include unwanted removal of metal or insulator layers and the corrosion of desirable metal layers, particularly copper or copper alloys features. Some prior art formulations employ corrosion inhibiting additives to prevent undesirable copper metal corrosion during the cleaning process. However, conventional corrosion-inhibiting additives typically have detrimental effects on the cleaning process because such additives interact with the residue and inhibit dissolution of such residue into the cleaning fluid. Moreover, conventional additives do not easily rinse off the copper surface after completion of the cleaning process. Such additives therefore remain on the surface sought to be cleaned, and result in contamination of the integrated circuits. Contamination of the integrated circuit can adversely increase the electrical resistance of contaminated areas and cause unpredictable conducting failure within the circuit.
The formulation of post CMP cleaners for advanced integrated circuit manufacturing such as copper and tungsten interconnect materials, includes slurry removal and residue dissolution components that accelerate the physical cleaning process. However, these conventional additives typically have detrimental effects on the metal surface by increasing resistance and corrosion sensitivity.
It is therefore one object of the present invention to provide chemical formulations that effectively remove residue following a resist ashing step, and which do not attack and potentially degrade delicate structures intended to remain on the wafer.
It is another object of the present invention to replace conventional additives with an improved corrosion inhibitor for protection of copper structures on the semiconductor substrate.
It is another object of the invention to provide an improved corrosion inhibitor, which is easily rinsed off the substrate by water or other rinse medium after the completion of the residue-removal process, thereby reducing contamination of the integrated circuit.
Other objects and advantages of the invention will become fully apparent from the ensuing disclosure and appended claims.
The present invention relates generally to chemical formulations useful in semiconductor manufacturing for removing residue from wafers following a resist plasma ashing step.
In one aspect, the invention relates to a method of removing residue from a wafer following a resist plasma ashing step on such wafer, comprising contacting the wafer with a cleaning formulation, including (i) a fluoride source, (ii) at least one organic amine, (iii) a nitrogen-containing carboxylic acid or an imine, (iv) water, and optionally at least one metal chelating agent.
Another aspect of the invention relates to a wafer cleaning formulation, including (i) a fluoride source, (ii) at least one organic amine, (iii) a nitrogen-containing carboxylic acid or an imine, (iv) water, and optionally at least one metal chelating agent.
In a further aspect, the invention relates to a semiconductor wafer cleaning formulation for use in post plasma ashing semiconductor fabrication, comprising the following components in the percentage by weight (based on the total weight of the formulation) ranges shown:
Such formulations of the invention effectively remove inorganic residues following a plasma ashing step.
Such formulations also effectively remove metal halide and metal oxide residues following plasma ashing, and effectively remove slurry particles of aluminum oxides and other oxides remaining after CMP (chemical mechanical polishing).
The formulations of the present invention provide better stripping performance with less corrosivity than formulations containing either ammonium fluoride or amines. Formulations in accordance with the invention also provide better stripping performance at lower processing temperatures than conventional amine-containing formulations.
The formulations of the invention utilize a chelating agent, which may be a single-component chelating agent or a multicomponent chelating agent, to prevent metal corrosion and increase stripping effectiveness.
Other features and advantages of the present invention will be from the ensuing disclosure and appended claims.